Prior art systems for data communication over electric power distribution lines, for example between a low-voltage transformer station and a house connection unit and/or within a house, commonly use at least one master station and slave modems which have to register to the master station. The same network architecture is also used for broadband data communications over the electricity distribution inside the house.
Such systems are based either on time division multiple access (TDMA) and/or use orthogonal frequency division multiplexing (OFDM) techniques. Although OFDM techniques allow for higher data rates than time division multiple access techniques, they have a major drawback in that they have poor stop-band attenuation.
Disadvantages of the master-slave approach are that the transmit level of the master station must be high enough to allow to reach the most distant slave modem and that the communication bandwidth must be shared between several slave modems.
Main disadvantages of the prior art systems for data communication over electric power distribution lines are:                a high transmit level needed to reach the most distant slave modem, resulting in corresponding electromagnetic radiation emissions,        complex random access schemes required to control the permission to transmit of the slave modems,        the master station represents a single point of failure, and        the need for time synchronization between different master stations to avoid interferences between the ongoing simultaneous power line communications, if several power line master-slave systems are used at the same time.        
These drawbacks are main barriers to the broad deployment of power line communication.